Memory devices are typically provided as internal, semiconductor, integrated circuits and/or external removable devices in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), flash memory, and resistive (e.g., resistance variable) memory, among others. Types of resistive memory include programmable conductor memory, phase change random access memory (PCRAM), resistive random access memory (RRAM), magnetoresistive random access memory (MRAM; also referred to as magnetic random access memory), and conductive-bridging random access memory (CBRAM), among others.
Memory devices can be utilized as volatile and non-volatile memory for a wide range of electronic applications in need of high memory densities, high reliability, and low power consumption. Non-volatile memory may be used in, for example, personal computers, portable memory sticks, solid state drives (SSDs), personal digital assistants (PDAs), digital cameras, cellular telephones, portable music players (e.g., MP3 players) and movie players, among other electronic devices. Data, such as program code, user data, and/or system data, such as a basic input/output system (BIOS), are typically stored in non-volatile memory devices.
Resistive memory such as RRAM includes resistive memory cells that can store data based on the resistance state of a storage element (e.g., a resistive memory element having a variable resistance). As such, resistive memory cells can be programmed to store data corresponding to a desired state by varying the resistance level of the resistive memory element. Resistive memory cells can be programmed to a target data state (e.g., corresponding to a particular resistance state) by applying sources of an electrical field or energy, such as positive or negative electrical pulses (e.g., positive or negative voltage or current pulses) to the cells (e.g., to the resistive memory element of the cells) for a particular duration.
One of a number of programmed states (e.g., resistance states) can be set for a resistive memory cell. For example, a single level cell (SLC) may be programmed to one of two data states (e.g., logic 1 or 0), which can depend on whether the cell is programmed to a resistance above or below a particular level. As an additional example, various resistive memory cells can be programmed to one of multiple different resistance states corresponding to multiple data states. Such cells may be referred to as multi state cells, multi-digit cells, and/or multilevel cells (MLCs), and can represent multiple binary digits of data (e.g., 10, 01, 00, 11, 111, 101, 100, 1010, 1111, 0101, 0001, etc.).
The data state of a resistive memory cell can be determined (e.g., read) by sensing current through the cell responsive to an applied interrogation voltage. The sensed current, which varies based on the resistance level of the cell, can indicate the data state of the cell. However, in previous resistive memory approaches (e.g., previous MLC resistive memory approaches), as a resistive memory cell undergoes sensing over time and/or disturb from programming and/or erase operations on adjacent cells, the resistance level of the cell (e.g., of the resistance memory element of the cell) may shift due to, for example, the formation of a weak conductive filament in the resistance memory element. Such a resistance shift can result in a drift of the sensed (e.g., read) current through the cell, which can result in an erroneous determination of the data state of the cell. For example, the sensed current drift can result in a determination that the cell is in a data state other than the target data state to which the cell was programmed.